Simultaneous data transmission between an access point and a plurality of stations

ABSTRACT

Provided is a wireless communication terminal. The wireless communication terminal includes a transceiver configured to transmit and receive a wireless signal and a processor configured to control an operation of the wireless communication terminal. The processor collects data to be transmitted to a plurality of terminals, generates an aggregate-MAC protocol data unit for transmitting data to the plurality of terminals at the same time, and transmits the aggregate-MAC protocol data unit to the plurality of terminals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/113,060, filed on Dec. 6, 2020, issued as U.S. Pat. No. 11,350,390dated May 31, 2022, which is a continuation of U.S. patent applicationSer. No. 16/892,283 filed on Jun. 4, 2020, issued as U.S. Pat. No.10,893,511 dated Jan. 12, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/112,542 filed on Aug. 24, 2018, issued as U.S.Pat. No. 10,708,890 dated Jul. 7, 2020, which is a continuation of U.S.patent application Ser. No. 15/322,720, filed on Dec. 28, 2016, issuedas U.S. Pat. No. 10,085,243 dated Sep. 25, 2018, which is the U.S.National Stage of International Patent Application No. PCT/KR2015/006770filed on Jul. 1, 2015, which claims the priority to Korean PatentApplication No. 10-2014-0081663 filed in the Korean IntellectualProperty Office on Jul. 1, 2014, and Korean Patent Application No.10-2014-0092329 filed in the Korean Intellectual Property Office on Jul.22, 2014, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal for setting a broadband link. Morespecifically, the present invention relates to a wireless communicationmethod and a wireless communication terminal for increasing datacommunication efficiency by expanding a data transmission bandwidth of aterminal.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelessLAN technology that can provide a rapid wireless Internet service to themobile apparatuses has been significantly spotlighted. The wireless LANtechnology allows mobile apparatuses including a smart phone, a smartpad, a laptop computer, a portable multimedia player, an embeddedapparatus, and the like to wirelessly access the Internet in home or acompany or a specific service providing area based on a wirelesscommunication technology in a short range.

Institute of Electrical and Electronics Engineers (IEEE) 802.11 hascommercialized or developed various technological standards since aninitial wireless LAN technology is supported using frequencies of 2.4GHz. First, the IEEE 802.11b supports a communication speed of a maximumof 11 Mbps while using frequencies of a 2.4 GHz band. IEEE 802.11a whichis commercialized after the IEEE 802.11b uses frequencies of not the 2.4GHz band but a 5 GHz band to reduce an influence by interference ascompared with the frequencies of the 2.4 GHz band which aresignificantly congested and improves the communication speed up to amaximum of 54 Mbps by using an OFDM technology. However, the IEEE802.11a has a disadvantage in that a communication distance is shorterthan the IEEE 802.11b. In addition, IEEE 802.11g uses the frequencies ofthe 2.4 GHz band similarly to the IEEE 802.11b to implement thecommunication speed of a maximum of 54 Mbps and satisfies backwardcompatibility to significantly come into the spotlight and further, issuperior to the IEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of a radiointerface accepted by 802.11n, such as a wider radio frequency bandwidth(a maximum of 160 MHz), more MIMO spatial streams (a maximum of 8),multi-user MIMO, and high-density modulation (a maximum of 256 QAM).Further, as a scheme that transmits data by using a 60 GHz band insteadof the existing 2.4 GHz/5 GHz, IEEE 802.11ad has been provided. The IEEE802.11ad is a transmission standard that provides a speed of a maximumof 7 Gbps by using a beamforming technology and is suitable for high bitrate moving picture streaming such as massive data or non-compression HDvideo. However, since it is difficult for the 60 GHz frequency band topass through an obstacle, it is disadvantageous in that the 60 GHzfrequency band can be used only among devices in a short-distance space.

Meanwhile, in recent years, as next-generation wireless LAN standardsafter the 802.11ac and 802.11ad, discussion for providing ahigh-efficiency and high-performance wireless LAN communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless LAN environment, communication havinghigh frequency efficiency needs to be provided indoors/outdoors underthe presence of high-density stations and access points (APs) andvarious technologies for implementing the communication are required.

DISCLOSURE Technical Problem

An object of the present invention is to provide an efficient wirelesscommunication method and wireless communication terminal.

Another object of the present invention is to provide a wirelesscommunication method and a wireless communication terminal allowingsimultaneous data transmission between a station and an AP.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, there isprovided a wireless communication terminal including: a transceiverconfigured to transmit and receive a wireless signal; and a processorconfigured to control an operation of the wireless communicationterminal, wherein the processor collects data to be transmitted to aplurality of terminals, generates an aggregate-MAC protocol data unitfor transmitting data to the plurality of terminals at the same time,and transmits the aggregate-MAC protocol data unit to the plurality ofterminals.

The transceiver may transmit a first frame indicating a transmissionpreparation of the aggregate-MAC protocol data unit.

The first frame may include a plurality of terminal identifiers foridentifying the plurality of respective terminals and the number of theplurality of terminals.

An arrangement order of the plurality of terminal identifiers mayindicate an arrangement order of channels allocated to the plurality ofterminals.

The transceiver may transmit the first frame through an availablechannel other than a primary channel and a secondary channel extendingthe primary channel.

The transceiver may transmit the first frame through one channel among aplurality of available channels and transmit a second frame indicating adata transmission preparation for one terminal through the remainingavailable channels except for the one channel.

The transceiver may transmit the aggregate-MAC protocol data unitthrough an available channel other than a primary channel and asecondary channel extending the primary channel.

The aggregate-MAC protocol data unit may include a plurality of MACprotocol data units and the first MAC protocol data unit among theplurality of MAC protocol data units may be a header for signaling datain the aggregate-MAC protocol data unit.

The header may include a group address for identifying a groupindicating the plurality of terminals.

The header may include information on a channel used by the wirelesscommunication terminal and a modulation and coding scheme (MCS) of asignal used in the channel.

The header may include user information indicating a relationshipbetween the plurality of MAC protocol data units in the aggregate MACprotocol data unit and the plurality of terminals.

According to another aspect of the present invention, there is provideda wireless communication terminal includes: a transceiver configured totransmit and receive a wireless signal; and a processor configured tocontrol an operation of the wireless communication terminal, wherein thetransceiver receives an aggregate-MAC protocol data unit fortransmitting data to a plurality of terminals at the same time, and theprocessor obtains a MAC protocol data unit relating to the wirelesscommunication terminal from the aggregate-MAC protocol data unit

The transceiver may receive a first frame indicating a transmissionpreparation of the aggregate-MAC protocol data unit.

The first frame may include a plurality of terminal identifiers foridentifying the plurality of respective terminals and the number of theplurality of terminals.

An arrangement order of the plurality of terminal identifiers mayindicate an arrangement order of channels allocated to the plurality ofterminals; the processor may determine a channel allocated to thewireless communication terminal based on the arrangement order of theplurality of terminal identifiers; and the transceiver may transmit acontrol frame to the wireless communication terminal transmitting theaggregate-MAC protocol data unit through the channel allocated to thewireless communication terminal.

An arrangement order of the plurality of terminal identifiers mayindicate a transmission order between the plurality of terminalstransmitting a control frame to a wireless communication terminaltransmitting the aggregate-MAC protocol data unit; the processor maydetermine a transmission order between the plurality of terminals basedon the arrangement order of the plurality of terminal identifiers; andthe transceiver may transmit the control frame to the wirelesscommunication terminal transmitting the aggregate-MAC protocol data unitthrough a channel allocated to the wireless communication terminal.

The plurality of terminals may transmit the control frame through onespecified channel.

The control frame may be a frame indicating that data transmission isavailable.

The processor may obtain information on a channel used by the wirelesscommunication terminal and a modulation and coding scheme (MCS) of asignal used in the channel based on the aggregate-MAC protocol dataunit.

According to a further another aspect of the present invention, there isprovided an operation method of a wireless communication terminalincluding: collecting data to be transmitted to a plurality ofterminals; generating an aggregate-MAC protocol data unit fortransmitting data to the plurality of terminals at the same time; andtransmitting the aggregate-MAC protocol data unit.

Advantageous Effects

According to the present invention, an embodiment provides an efficientwireless communication method and wireless communication terminal.

Especially, an embodiment of the present invention provides a wirelesscommunication method and a wireless communication terminal allowingsimultaneous data transmission between an access point and a pluralityof stations.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a wireless LAN system according to anembodiment of the present invention.

FIG. 2 is a view illustrating a wireless LAN system according to anotherembodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a stationaccording to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 is a view illustrating a process that a station sets an accesspoint and a link according to an embodiment of the present invention.

FIG. 6 is a view illustrating the header of an aggregate-MAC protocoldata unit for transmitting data to a plurality of terminals at the sametime according to an embodiment of the present invention.

FIG. 7 is a view of allocating a primary channel and a secondary channelto a plurality of terminals to transmit an aggregate-MAC protocol dataunit for transmitting data to a plurality of terminals at the same timeaccording to an embodiment of the present invention.

FIGS. 8 to 11 are views that an access point transmits data to aplurality of stations through an aggregate-MAC protocol data unit fortransmitting data to a plurality of terminals at the same time accordingto an embodiment of the present invention.

FIG. 12 is a view illustrating the structure of a frame indicating thesimultaneous transmission preparation of a plurality of stations whendata is transmitted to a plurality of terminals at the same timeaccording to another embodiment of the present invention.

FIGS. 13 to 20 are views that an access point transmits data to aplurality of stations at the same time through a frame indicating thesimultaneous transmission preparation for a plurality of stationsaccording to another embodiment of the present invention.

FIGS. 21 to 23 are views that an access point transmits data to aplurality of stations at the same time without transmitting a frameindicating the data transmission preparation according to anotherembodiment of the present invention.

FIG. 24 is a ladder diagram illustrating an operation that a terminaltransmits data to a plurality of other terminals at the same timeaccording to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2014-0081663, and 10-2014-0092329 filed in theKorean Intellectual Property Office and the embodiments and mentioneditems described in the respective applications are included in theDetailed Description of the present application.

FIG. 1 is a diagram illustrating a wireless LAN system according to anembodiment of the present invention. The wireless LAN system includesone or more basic service sets (BSS) and the BSS represents a set ofapparatuses which are successfully synchronized with each other tocommunicate with each other. In general, the BSS may be classified intoan infrastructure BSS and an independent BSS (IBSS) and FIG. 1illustrates the infrastructure BSS between them.

As illustrated in FIG. 1 , the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STA5, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a radio medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless LAN systemaccording to another embodiment of the present invention. In theembodiment of FIG. 2 , duplicative description of parts, which are thesame as or correspond to the embodiment of FIG. 1 , will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3 , the station 100 according to the embodimentof the present invention may include a processor 110, a transceiver 120,a user interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a radio signal such asa wireless LAN packet, or the like and may be embedded in the station100 or provided as an exterior. According to the embodiment, thetransceiver 120 may include at least one transmit/receive module usingdifferent frequency bands. For example, the transceiver 120 may includetransmit/receive modules having different frequency bands such as 2.4GHz, 5 GHz, and 60 GHz. According to an embodiment, the station 100 mayinclude a transmit/receive module using a frequency band of 6 GHz ormore and a transmit/receive module using a frequency band of 6 GHz orless. The respective transmit/receive modules may perform wirelesscommunication with the AP or an external station according to a wirelessLAN standard of a frequency band supported by the correspondingtransmit/receive module. The transceiver 120 may operate only onetransmit/receive module at a time or simultaneously operate multipletransmit/receive modules together according to the performance andrequirements of the station 100. When the station 100 includes aplurality of transmit/receive modules, each transmit/receive module maybe implemented by independent elements or a plurality of modules may beintegrated into one chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 controls various operations of radio signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4 , the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4 , among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4 , the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3 , thetransceiver 220 of the AP 200 may also include a plurality oftransmit/receive modules using different frequency bands. That is, theAP 200 according to the embodiment of the present invention may includetwo or more transmit/receive modules among different frequency bands,for example, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200may include a transmit/receive module using a frequency band of 6 GHz ormore and a transmit/receive module using a frequency band of 6 GHz orless. The respective transmit/receive modules may perform wirelesscommunication with the station according to a wireless LAN standard of afrequency band supported by the corresponding transmit/receive module.The transceiver 220 may operate only one transmit/receive module at atime or simultaneously operate multiple transmit/receive modulestogether according to the performance and requirements of the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 controls variousoperations such as radio signal transmission/reception of the AP 200according to the embodiment of the present invention. A detailedembodiment thereof will be described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5 , the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5 , the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

When data is transmitted using Orthogonal Frequency Division MultipleAccess (OFDMA), any one terminal may transmit data to a plurality ofterminals simultaneously. However, a frequency channel that a terminaltransmitting data uses is limited. Therefore, a terminal transmittingdata is required to efficiently allocate an available frequency channeland transmit the data. In addition, the sizes of data that a terminaltransmitting data transmits to a plurality of terminals at the same timemay be all different. Therefore, it may be inefficient to allocatefrequency channels of the same size to all terminals receiving data.When a terminal transmitting data aggregates data to be transmitted to aplurality of terminals and transmits the aggregated data to theplurality of terminals at the same time by using all available frequencychannels, it may use an available frequency without waste. Additionally,in this case, a terminal transmitting data is not required to perform acomplicated operation for allocating an available frequency channel toeach terminal receiving data. Accordingly, a data transmission methodthrough an aggregate-MAC protocol data unit where a plurality of MACprotocol data units including data to be transmitted to a plurality ofterminals are aggregated is required. At this point, an aggregate-MACprotocol data unit for transmitting data to a plurality of terminals atthe same time is different from an existing aggregate-MAC protocol dataunit (A-MPDU) that aggregates MPDUs to be transmitted to the sameaddress and transmits MPDUs. Accordingly, an aggregate-MAC protocol dataunit for transmitting data to a plurality of terminals at the same timeis referred to as plural terminal A-MPDUs or plural station A-MPDUs.Additionally, a terminal for transmitting data to a plurality ofterminals using OFDMA is referred to as a transmission terminal and eachof a plurality of terminals for receiving data at the same time usingOFDMA is referred to as a reception terminal. At this point, data that atransmission terminal transmits and a reception terminal receives isreferred to as plural terminal data. At this point, a transmissionterminal may transmit different data corresponding to each receptionterminal to each of a plurality of reception terminals at the same time.Additionally, the plurality of terminal data may be the plural terminalA-MPDUs described above. In a specific embodiment, a transmissionterminal may be an access point. Additionally, a reception terminal maybe a station associated with an access point. Transmitting data to aplurality of terminals using OFDMA will be described with reference toFIGS. 6 to 24 .

FIG. 6 is a view illustrating the header of an aggregate-MAC protocoldata unit for transmitting data to a plurality of terminals at the sametime according to an embodiment of the present invention.

A plurality of terminal data may include a header for signaling data inthe plurality of terminal data. In a specific embodiment, pluralterminal A-MPDUs may include a plurality of MAC protocol data units(MPDUs) to be transmitted to a plurality of terminals. The pluralterminal A-MPDUs may include a header for signaling data in the pluralterminal A-MPDUs. Specifically, the header of the plural terminalA-MPDUs may be one MPDU. Additionally, such a header may be positionedat the first of the plural terminal A-MPDUs. Accordingly, a receptionterminal may obtain information on data that the plural terminal A-MPDUsinclude by obtaining the first MPDU in the plural terminal A-MPDUs.Additionally, the headers of a plurality of terminal data may betransmitted through a predetermined modulation and coding scheme (MCS).Through this, a reception terminal may receive information on aplurality of terminal data signaled by a header by decoding the headerthrough a predetermined MCS without additional information. For example,when a header is specified to be transmitted through BPSK 1/2 and is oneMPDU that is positioned at the first of plural terminal A-MPDUs, areception terminal sets an MCS to BPSK 1/2 and decodes the first MPDU ofthe plural terminal A-MPDUs to obtain a header.

The headers of a plurality of terminal data may include a group addressfor identifying a group that represents a plurality of receptionterminals. At this point, a reception terminal may receive a pluralityof terminal data based on the group address. Specifically, when thegroup address represents a group to which the reception terminalbelongs, the reception terminal may receive a plurality of terminaldata. Specifically, the group address may be an identifier indicatingthe addresses of a plurality of terminals that receive signals usingOFDMA. At this point, a group identifier may be referred to as an OFDMAgroup address. Additionally, the headers of a plurality of terminal datamay include information on a channel and an MCS of a signal used in thechannel. In more detail, the headers of a plurality of terminal data mayinclude information on a channel that a transmission terminal uses. Inaddition, the headers of a plurality of terminal data may includeinformation on a channel that another terminal which is different from atransmission terminal is using and is thus not allocated. Additionally,the headers of a plurality of terminal data may include information on achannel that transmits signals through the same MCS. Accordingly, areception terminal may receive a plurality of terminal data based oninformation on a channel and the MCS of a signal used in the channel. Inaddition, the header may include a terminal identifier for identifying areception terminal. At this point, the terminal identifier may be anidentifier for identifying a station. For example, the terminalidentifier may be an Association ID (AID) assigned from an AP during anassociation process between an STA and the AP and identifying anassociation between the STA and the AP. In addition, the terminalidentifier may be a short-AID (S-AID), which is simply made using onlythe lower 8 bits of the AID. In addition, the headers of a plurality ofterminal data may include user information indicating a relationshipbetween data in the plurality of terminal data and a plurality ofreception terminals. Specifically, the user information may include thenumber of reception terminals. In addition, the user information mayinclude an arrangement order of MPDUs including data corresponding tothe reception terminal. In a specific embodiment, the arrangement orderof a terminal identifier in the headers of a plurality of terminal datamay represent the arrangement order of data corresponding to a terminalthat the terminal identifier represents among a plurality of data in aplurality of terminal data. For example, when the header includesinformation on a terminal identifier in the order of a terminalidentifier for a first terminal and a terminal identifier for a secondterminal, data on the first terminal may be positioned first and data onthe second terminal may be positioned following that. In anotherspecific embodiment, the user information may include the identifier ofa terminal and offset information representing the position of dataincluding data on a corresponding terminal. For example, when offsetinformation on the first terminal indicates 0 byte and offsetinformation on the second terminal indicates 12 bytes, data includingdata on the second terminal may be positioned after 12 bytes from theheaders of a plurality of terminal data. Through such a specificembodiment, a reception terminal may extract data relating to thereception terminal from a plurality of terminal data based on arelationship between a plurality of data in the plurality of terminaldata and a plurality of terminals that are to receive the plurality ofterminal data. However, when an S-AID is used as a terminal identifieras described above, S-AIDs for different terminals may be identical toeach other. In such a case, after the reception terminal extracts datacorresponding to its own S-AID from the plurality of terminal data, thereception terminal is required to check whether data on itself iscorrect through the header included in the extracted data.

Specifically, the syntax of the header of the plurality of terminal datamay be obtained by modifying the syntax of the MPDU of the existing802.11ac standard as shown in FIG. 6 . Specifically, an Address 1 fieldmay represent the group identifier described above. Additionally, areserved bit field that is a bit positioned at the first part of the HTControl Middle field may represent that a corresponding MPDU is theheaders of a plurality of terminal data. Specifically, when the reservedbit field is 1, this field may indicate that a corresponding MPDU is theheader of the plurality of terminal data. Specifically, the reserved bitfield may indicate that transmission information (e.g., an OFDMAcontrol) on a plurality of terminals including a variable-lengthallocation bitmap and a user indication is included. In a specificembodiment, the reserved bit may be referred to as an OFDMA control bit.

Additionally, a Body field including data that an MPDU transmits mayinclude information for signaling a plurality of terminal data.Specifically, the Body field including data that an MPDU transmits mayinclude an Allocation Bitmap field indicating information on a channeland an MCS of a signal used in the channel. The Allocation Bitmap fieldmay be divided into a plurality of channel (CH) fields, and each of theplurality of CH fields may indicate an MCS of a signal used in thecorresponding channel. Specifically, each of the plurality of CH fieldsmay include index information indicating an MCS of a signal used in thechannel. At this time, the index information may indicate that the otherterminal uses a channel currently and the channel is unavailable. In aspecific embodiment, the Allocation Bitmap field may be a 4-byte field.In addition, each CH field is a 4-bit field, and the Allocation Bitmapfield may include 8 CH fields. Additionally, a transmission terminal maysimultaneously transmit a plurality of terminal data to a plurality ofterminals through a channel through which signals having the same MCSare transmitted. Specifically, a transmission terminal may transmit apiece of a plurality of terminal data through a plurality of channelsthrough which signals having the same MCS are transmitted. Specifically,the index information may be the same as the MCS index information ofFIG. 6 . For example, if the 8 CH fields in the Allocation Bitmap fieldhave values of 0001, 0001, 0001, 0011, 0011, 1111, 1111 and 0101,respectively, a transmission terminal modulates signals through QPSK 1/2and transmits one of the plural terminal A-MPDUs through CH 1, CH 2, andCH 3. At this point, the transmission terminal modulates signals throughQPSK 3/4 and transmits one A-MPDU through CH 4 and CH 5. At this point,CH 6 and CH 7 as busy channels indicate that they are being used byother terminals. In addition, the transmission terminal modulatessignals through 64-QAM 2/3 and transmits plural terminal A-MPDUs throughCH 8.

In addition, the Body field may include a User Indication fieldindicating a relationship between a plurality of data included in aplurality of terminal data and a plurality of reception terminals.Specifically, the User Indication field may include a user field #Userindicating the number of all terminals to receive a plurality ofterminal data and a field indicating a terminal identifier foridentifying a terminal. As described above, the arrangement order ofterminal identifiers may indicate the arrangement order of datacorresponding to a terminal indicated by a terminal identifier among aplurality of data in a plurality of terminal data. In addition, theterminal identifier may be an Association ID (AID) assigned from an APduring an association process between an STA and the AP and identifyingan association between the STA and the AP. In addition, the terminalidentifier may be a short-AID (S-AID), which is simply made using onlythe lower 8 bits of the AID.

The headers of a plurality of terminal data may be referred to as anOFDMA header. At this point, the above-described group identifier may bean identifier indicating the addresses of a plurality of terminals thatreceive a signal using OFDMA. At this point, the group identifier may bereferred to as an OFDMA group address.

FIG. 7 is a view of allocating a primary channel and a secondary channelto a plurality of terminals to transmit an aggregate-MAC protocol dataunit for transmitting data to a plurality of terminals at the same timeaccording to an embodiment of the present invention.

As described above, a transmission terminal may perform OFDMAtransmission for transmitting data simultaneously to a plurality ofterminals through a channel through which signals having the same MCS istransmitted. Specifically, a transmission terminal may transmit aplurality of terminal data through a plurality of frequency channelsthrough which signals using the same MCS are transmitted. Also, thetransmission terminal may transmit a plurality of terminal data usingall available frequency channels. At this point, the transmissionterminal may transmit a signal including information relating to dataencoding after transmitting the preamble of a wireless signal. Theinformation relating to data encoding may include an MCS. In addition,the transmission terminal may transmit a signal including informationrelating to data encoding by a unit of 20 MHz. Such a signal is referredto as AX-SIG. The reception terminal may receive plural terminal A-MPDUsbased on AX-SIG. Specifically, the reception terminal may determine thata channel through which signals using the same MCS is transmitted is achannel through which a plurality of terminal data is transmitted. Inaddition, the reception terminal may determine that a channel in whichthe preamble and AX-SIG are not detected is a channel not allocated to aterminal. Accordingly, when decoding, the reception terminal may excludethe channel from which the preamble and AX-SIG are not detected. Also,as described above, the transmission terminal may insert the informationrelating to data encoding in the header of the plurality of terminaldata to transmit the information relating to data encoding. At thispoint, the reception terminal may obtain the information relating toencoding based on the header of the plurality of terminal data.Specifically, the reception terminal may obtain the information on MCSbased on the header of the plurality of terminal data. Additionally, thereception terminal may obtain the information on an unallocated channelbased on the header of the plurality of terminal data. Specifically, thereception terminal may obtain information relating to data encodingbased on information on a channel in the headers of a plurality ofterminal data and an MCS of a signal transmitted from the channel. Forexample, the reception terminal may obtain the information relating toencoding based on the Allocation Bitmap field in the headers of aplurality of terminal data. At this point, the plurality of terminaldata may be the plural terminal A-MPDUs.

In the embodiment of FIG. 7 , signals using the same MCS are transmittedfrom a primary channel Primary CH, a first secondary channel SecondaryCH #1, and a third secondary channel Secondary CH #3. Also, signalsusing the same MCS are transmitted from a fifth secondary channelSecondary CH #5, a sixth secondary channel Secondary CH #6, and aseventh secondary channel Secondary CH #7. Also, as in theabove-described embodiment, the headers of plural terminal A-MPDUs aretransmitted first among data in the plural terminal A-MPDUs. At thispoint, a reception terminal may obtain information on the plurality ofMPDUs in the plural terminal A-MPDUs by extracting the first MPDU in theplural terminal A-MPDUs. Specifically, the reception terminal mayextract the first MPDU in the plural terminal A-MPDUs to obtaininformation on a channel and an MCS used by a signal transmitted to thechannel. In addition, the reception terminal may know information on theposition of an MPDU including data on the reception terminal. Throughthis, the reception terminal may know whether the data in the MPDU isrelated to the reception terminal without decoding the header of theMPDU. However, as described above, when an S-AID is used as a terminalidentifier, the S-AID for the different terminals may be the same. Inthis case, the reception terminal may decode the header of the MPDU todetermine whether the MPDU contains data on the reception terminal.

FIGS. 8 to 11 are views that an access point transmits data to aplurality of stations through an aggregate-MAC protocol data unit fortransmitting data to a terminal at the same time according to anembodiment of the present invention.

A transmission terminal may transmit a plurality of terminal data usingonly a secondary channel instead of a primary channel in considerationof compatibility with a legacy terminal using the prior art.Specifically, a transmission terminal may transmit a plurality ofterminal data using a secondary channel other than a secondary channelthat extends a primary channel among a plurality of secondary channels.A terminal using a conventional technique such as 802.11ac transmitsdata only through a primary channel or an extended channel in which aprimary channel and a secondary channel are connected. Accordingly whenonly a secondary channel other than a primary channel is used or asecondary channel other than a secondary channel extending a primarychannel is used to transmit a plurality of terminal data, data may betransmitted to both a terminal according to an embodiment of the presentinvention and a terminal that does not support an embodiment of thepresent invention. The specific operation of a terminal may be asfollows.

The transmission terminal may collect data to be transmitted for apredetermined time. Such a predetermined time may be referred to as aData Accumulation Timer. At this point, the transmission terminal maywait without transmitting data even if a channel is in an idle stateduring the Data Accumulation Timer. After collecting data to betransmitted, the transmission terminal obtains a channel to be used intransmission according to a contention method. Specifically, when achannel is in an idle state for a predetermined time, the transmissionterminal transmits a Ready To Send (RTS) frame, which is a frameindicating data transmission prepared after waiting for a contentionwindow value, to a plurality of channels. At this point, thepredetermined time may be Distributed Inter-Frame Space (DIFS) definedby the 802.11 standard. At this point, the transmission terminaltransmits an RTS frame for a legacy terminal through a primary channel,and an RTS frame for a terminal supporting an embodiment of the presentinvention may be transmitted through a secondary channel other than aprimary channel. Alternatively, the transmission terminal transmits anRTS frame for a legacy terminal through a primary channel and asecondary channel that extends a primary channel, and an RTS frame for aterminal supporting an embodiment of the present invention may betransmitted through a secondary channel other than a secondary channelextending a primary channel among a plurality of secondary channels.Additionally, the reception terminal may receive signals transmittedfrom all channels. In addition, the reception terminal may determinewhether its address is identical to a Receiver Address (RA) of an RTSframe. If its address is identical to the receiver address (RA) of theRTS frame, the reception terminal receiving the RTS frame may transmit aClear To Send (CTS) frame indicating that data transmission is availableafter a predetermined time from a time point at which the RTS frame istransmitted in response to the RTS frame. At this point, thepredetermined time may be a Short Inter-Frame Space (SIFS). Thetransmission terminal transmits data to a plurality of terminals after apredetermined time from the CTS frame in response to the CTS frame. Atthis point, the predetermined time may be an SIFS. At this point, thetransmission terminal may transmit data for a legacy terminal through aprimary channel, and transmit data for a terminal supporting anembodiment of the present invention to a plurality of terminal datathrough a secondary channel. Alternatively, the transmission terminalmay transmit data for a legacy terminal through a primary channel and asecondary channel extending the primary channel. At this point, thetransmission terminal may transmit data for a terminal supporting anembodiment of the present invention as a plurality of terminal datathrough a secondary channel other than a secondary channel that extendsa primary channel among a plurality of secondary channels. In moredetail, the transmission terminal may transmit data for a terminalsupporting an embodiment of the present invention as a plurality ofterminal data through a plurality of secondary channels other than asecondary channel that extends a primary channel among a plurality ofsecondary channels. At this point, the plurality of terminal data may bethe plural terminal A-MPDUs. The transmission terminal may determinewhether a channel is in an idle state for a predetermined time beforetransmitting the data to determine whether the channel is available ornot. At this point, the predetermined time may be a Point Inter-FrameSpace (PIFS). In addition, when it is determined that the channel isavailable, the transmission terminal may transmit data through acorresponding channel. The reception terminal that receives the data maytransmit an ACK frame indicating data reception completion. In addition,if data to be transmitted remains, the transmission terminal maydetermine a channel state again and transmit the remaining data. At thispoint, the transmission terminal may resume the transmission procedureof a plurality of terminal data by transmitting an RTS frame after apredetermined time after transmitting the ACK frame. In another specificembodiment, a channel to be used in transmission is obtained dependingon a contention method. Specifically, when a channel is in an idle statefor a predetermined time, the transmission terminal transmits a Ready ToSend (RTS) frame, which is a frame indicating data transmissionprepared, to a plurality of channels, after waiting for a contentionwindow value. At this point, the predetermined time may be DistributedInter-Frame Space (DIFS) defined by the 802.11 standard.

FIG. 8 is a view illustrating the transmission of plural terminalA-MPDUs through only a secondary channel other than a primary channelaccording to an embodiment of the present invention.

The numbers written in the frames of the drawing in this specificationindicate numbers for stations that receive or transmit correspondingframes. For example, an RTS frame received by a first station isindicated by RTS1, and a CTS frame transmitted by the first station isdenoted by CTS1.

In the embodiment of FIG. 8 , a transmission terminal is an accesspoint. Also, terminals receiving data from a terminal that transmitsplural terminal A-MPDUs are a first station, a second station, a thirdstation, a fourth station, a fifth station, a sixth station, a seventhstation, and an eighth station. At this point, the third station and thefifth station are legacy terminals that do not support an embodiment ofthe present invention. The access point transmits data to the thirdstation and the fifth station that do not support an embodiment of thepresent invention through a primary channel Primary CH. Specifically,the access point transmits an RTS frame to the third station that doesnot support an embodiment of the present invention through a primarychannel Primary CH. Then, the access point receives a CTS frame from thethird station through the primary channel Primary CH. The access pointtransmits data to the third station through the primary channel PrimaryCH. After the transmission to the third station is completed, the accesspoint transmits an RTS frame to the fifth station through the primarychannel Primary CH. Then, the access point receives a CTS frame from thefifth station through the primary channel Primary CH. The access pointtransmits data to the fifth station through the primary channel PrimaryCH. In addition, the access point transmits plural terminal A-MPDUs tothe first station, the second station, the fourth station, the sixthstation, the seventh station, and the eighth station, which support anembodiment of the present invention, by using an available secondarychannel. Specifically, the access point transmits plural terminalA-MPDUs including data for the first station and the second stationthrough the first secondary channel Secondary CH #1 and the secondsecondary channel Secondary CH #2. Specifically, the access pointtransmits an RTS frame to the first station and the second station,which support an embodiment of the present invention, through the firstsecondary channel Secondary CH #1 and the second secondary channelSecondary CH #2. Then, the access point receives a CTS frame through thefirst secondary channel Secondary CH #1 and the second secondary channelSecondary CH #2. The access point transmits plural terminal A-MPDUsincluding data for the first station and the second station to the firststation and the second station through the first secondary channelSecondary CH #1 and the second secondary channel Secondary CH #2.Additionally, the access point transmits the plural terminal A-MPDUs tothe fourth station through the fourth secondary channel Secondary CH #4.After the data transmission to the first station, the second station,and the fourth station is completed, the access point determines anavailable channel again and transmits data for the seventh station andthe eighth station. Specifically, the access point transmits pluralterminal A-MPDUs including data for the seventh station and the eighthstation to the seventh station and the eighth station through the secondsecondary channel Secondary #2 and the third secondary channel Secondary#3.

FIG. 9 is a view illustrating the transmission of plural terminalA-MPDUs through a secondary channel other than a secondary channelextending a primary channel among a plurality of secondary channelsaccording to an embodiment of the present invention.

In the embodiment of FIG. 9 , a transmission terminal is an accesspoint. Also, terminals receiving data from a terminal that transmitsplural terminal A-MPDUs are a first station, a second station, a thirdstation, a fourth station, a fifth station, a sixth station, and aseventh station. At this point, the third station and the fifth stationare legacy terminals that do not support an embodiment of the presentinvention. The access point transmits data to the third station and thefifth station that do not support an embodiment of the present inventionthrough a primary channel Primary CH and a first secondary channelSecondary CH #1 extending the Primary channel Primary CH. Specifically,the access point transmits an RTS frame to the third station that doesnot support an embodiment of the present invention through the primarychannel Primary CH and the first secondary channel Secondary CH #1.Then, the access point receives a CTS frame from the third stationthrough the primary channel Primary CH and the first secondary channelSecondary CH #1. Additionally, the access point transmits data to thethird station through the primary channel Primary CH and the firstsecondary channel Secondary CH #1. After the transmission to the thirdstation is completed, the access point transmits an RTS frame to thefifth station through the primary channel Primary CH and the firstsecondary channel Secondary CH #1. Then, the access point receives a CTSframe from the fifth station through the primary channel Primary CH andthe first secondary channel Secondary CH #1. Additionally, the accesspoint transmits data to the fifth station through the primary channelPrimary CH and the first secondary channel Secondary CH #1. In addition,the access point transmits plural terminal A-MPDUs to the first station,the second station, the fourth station, the sixth station, and theseventh station, which support an embodiment of the present invention,by using an available secondary channel. Specifically, the access pointtransmits plural terminal A-MPDUs including data for the first stationthrough the second secondary channel Secondary CH #2. Specifically, theaccess point transmits an RTS frame to the first station supporting anembodiment of the present invention through the second secondary channelSecondary CH #2. Then, the access point receives a CTS frame from thefirst station through the second secondary channel Secondary CH #2. Theaccess point transmits plural terminal A-MPDUs including data for thesecond station to the second station through the second secondarychannel Secondary CH #2. Additionally, the access point transmits theplural terminal A-MPDUs to the second station through the fourthsecondary channel Secondary CH #4. After the data transmission to thefirst station and the second station is completed, the access pointdetermines an available channel again and transmits data for the fourthstation, the sixth station, and the seventh station. Specifically, theaccess point transmits plural terminal A-MPDUs for the fourth station,the sixth station, and the seventh station through the second secondarychannel Secondary #2, the third secondary channel Secondary #3, and thefourth secondary channel Secondary #4.

FIG. 10 is a view illustrating that a channel for transmitting pluralterminal A-MPDUs extends dynamically based on an available channelaccording to an embodiment of the present invention.

In the embodiment of FIG. 10 , a transmission terminal is an accesspoint. Also, terminals receiving data from the transmission terminal area first station, a second station, a third station, a fourth station, afifth station, a sixth station, and a seventh station. At this point,the third station and the fifth station are legacy terminals that do notsupport an embodiment of the present invention. The access pointtransmits data to the third station that does not support an embodimentof the present invention through the primary channel Primary CH and thefirst secondary channel Secondary CH #1 extending the Primary channelPrimary CH and also transmits data to the fifth station through thePrimary channel Primary CH. Specifically, the access point transmits anRTS frame to the third station that does not support an embodiment ofthe present invention through the primary channel Primary CH and thefirst secondary channel Secondary CH #1. Then, the access point receivesa CTS frame from the third station through the primary channel PrimaryCH and the first secondary channel Secondary CH #1. The access pointtransmits data to the third station through the primary channel PrimaryCH and the first secondary channel Secondary CH #1. The access pointtransmits an RTS frame to the fifth station through the primary channelPrimary CH. Then, the access point receives a CTS frame from the fifthstation through the primary channel Primary CH. The access pointtransmits data to the fifth station through the primary channel PrimaryCH. In addition, the access point transmits plural terminal A-MPDUs tothe first station, the second station, the fourth station, the sixthstation, and the seventh station, which support an embodiment of thepresent invention, by using an available secondary channel.Specifically, the access point transmits plural terminal A-MPDUsincluding data for the second station to the second station through thesecond secondary channel Secondary CH #2. Specifically, the access pointtransmits an RTS frame to the first station supporting an embodiment ofthe present invention through the second secondary channel Secondary CH#2. Then, the access point receives a CTS frame from the first stationthrough the second secondary channel Secondary CH #2. The access pointtransmits plural terminal A-MPDUs including data for the first stationto the first station through the second secondary channel Secondary CH#2. In addition, the access point transmits plural terminal A-MPDUsincluding data for the second station to the second station through thefourth secondary channel Secondary CH #4. After the data transmission tothe first station and the second station is completed, the access pointdetermines an available channel again and transmits data for the fourthstation, the sixth station, and the seventh station. Specifically, theaccess point transmits plural terminal A-MPDUs for the fourth station,the sixth station, and the seventh station through the first secondarychannel Secondary #1, the second secondary channel Secondary #2, thethird secondary channel Secondary #3, and the fourth secondary channelSecondary #4, which are available during RTS frame transmission.Specifically, when transmitting data for the fourth station, the sixthstation, and the seventh station, the access point identifies anavailable channel again to transmit an RTS frame, and receives a CTSframe. After receiving the CTS frame, the access point transmits pluralterminal A-MPDUs through an available channel. The access point, asdescribed above, may determine that a corresponding channel is availablewhen the corresponding channel is in an idle state during a PIFS.

FIG. 11 is a view illustrating that a channel for transmitting pluralterminal A-MPDUs may be changed dynamically based on an availablechannel.

In the embodiment of FIG. 11 , a transmission terminal is an accesspoint. Also, terminals receiving data from the transmission terminal area first station, a second station, a third station, a fourth station, afifth station, a sixth station, a seventh station, an eighth station, aninth station, and a tenth station. The access point transmits pluralterminal A-MPDUs to the first station, the second station, the thirdstation, the fourth station, the fifth station, the sixth station, andthe seventh station by using a primary channel Primary CH and aplurality of available secondary channels. Specifically, the accesspoint transmits plural terminal A-MPDUs to the first station, the secondstation, the third station, the fourth station, the fifth station, thesixth station, and the seventh station through the primary channelPrimary CH, the first secondary channel Secondary CH #1, the secondsecondary channel Secondary CH #2, the fourth secondary channelSecondary CH #4, the fifth secondary channel Secondary CH #5, the sixthsecondary channel Secondary CH #6, and the seventh secondary channelSecondary CH #7. Specifically, the access point transmits an RTS frameto the first station, the second station, the third station, the fourthstation, the fifth station, the sixth station, and the seventh stationthrough the primary channel Primary CH, the first secondary channelSecondary CH #1, the second secondary channel Secondary CH #2, thefourth secondary channel Secondary CH #4, the fifth secondary channelSecondary CH #5, the sixth secondary channel Secondary CH #6, and theseventh secondary channel Secondary CH #7. The access point receives aCTS frame from the first station, the second station, the third station,the fourth station, the fifth station, the sixth station, and theseventh station through the primary channel Primary CH, the firstsecondary channel Secondary CH #1, the second secondary channelSecondary CH #2, the fourth secondary channel Secondary CH #4, the fifthsecondary channel Secondary CH #5, the sixth secondary channel SecondaryCH #6, and the seventh secondary channel Secondary CH #7. The accesspoint transmits plural terminal A-MPDUs to the first station, the secondstation, the third station, the fourth station, the fifth station, thesixth station, and the seventh station through the primary channelPrimary CH, the first secondary channel Secondary CH #1, the secondsecondary channel Secondary CH #2, the fourth secondary channelSecondary CH #4, the fifth secondary channel Secondary CH #5, the sixthsecondary channel Secondary CH #6, and the seventh secondary channelSecondary CH #7. At this point, the access point may divide the pluralterminal A-MPDUs into two to transmit the divided the plural terminalA-MPDUs. Specifically, the access point may transmit plural terminalA-MPDUs including data for the first station, the second station, andthe third station through the primary channel Primary CH, the firstsecondary channel Secondary CH #1 and the second secondary channelSecondary CH #2, and transmit plural terminal A-MPDUs including data forthe fourth station, the fifth station, the sixth station, and theseventh station through the fourth secondary channel Secondary CH #4,the fifth secondary channel Secondary CH #5, the sixth secondary channelSecondary CH #6, and the seventh secondary channel Secondary CH #7.After the data transmission to the first station, the second station,the fourth station, the fifth station, the sixth station, and theseventh station is completed, the access point determines an availablechannel again and transmits data for the eighth station, the ninthstation, and the tenth station. Specifically, the access pointdetermines an available channel before transmitting an RTS frame. Asdescribed above, the access point may determine that a channel isavailable when the channel is in an idle state during a PIFS. The accesspoint transmits plural terminal A-MPDUs for the eighth station and theninth station through the primary channel Primary CH and the firstsecondary channel Secondary CH #1. At this point, the access pointdetermines that the third secondary channel Secondary #3, which wasunavailable at the time of the first transmission of the plural terminalA-MPDUs, becomes available, and transmits the plural terminal A-MPDUsfor the tenth station through the third secondary channel Secondary #3.

In the embodiments of FIGS. 9 to 11 , the transmission terminal reservesa channel for transmitting a plurality of terminal data by using aconventional RTS frame and transmits the plurality of terminal data. Insuch a case, the transmission is required to transmit RTS frames by asmany as the number of reception terminals so that the receptionterminals recognize that data is transmitted. In addition, there is aproblem that the reception terminals do not recognize whether theyreceive general data or a plurality of terminal data. Therefore, a newtype of frame indicating the transmission preparation of a plurality ofterminal data is required. This will be described with reference toFIGS. 12 to 20 .

FIG. 12 is a view illustrating the structure of a frame indicating thetransmission preparation of a plurality of terminal data when data istransmitted to a plurality of terminals at the same time according toanother embodiment of the present invention.

A frame indicating the transmission preparation of a plurality ofterminal data according to an embodiment of the present invention isreferred to as an Aggregation-RTS (A-RTS) frame. The A-RTS frame mayinclude a terminal identifier field indicating a terminal identifier foridentifying a reception terminal. Specifically, the terminal identifierfiled may indicate the address of a terminal. In another specificembodiment, the terminal identifier field may indicate an Association ID(AID) allocated in an association process between a terminal and aterminal. In addition, an A-RTS frame may include a number field of aterminal indicating the number of reception terminals. In addition, theA-RTS frame may include information on a channel that the receptionterminal is to use. Specifically, the arrangement order of terminalidentifiers in the identifier field in the A-RTS frame may indicate thearrangement order of channels allocated to a terminal indicated by aterminal identifier. At this point, the reception terminal may transmita CTS frame through an allocated channel. In addition, the receptionterminal may transmit an ACK frame through the allocated channel. Forexample, when an identifier indicating the first station is located andan identifier indicating the second station is located thereafter in theterminal identifier field, the first station transmits a CTS frame andan ACK frame using a primary channel and the second station transmits aCTS frame and an ACK frame using a first secondary channel. In addition,the A-RTS frame may include a field indicating a relationship of an MPDUin a plurality of terminal data and a reception terminal. In a specificembodiment, the arrangement order of terminal identifiers indicated bythe terminal identifier field of an A-RTS frame may indicate thearrangement order of data corresponding to a terminal indicated by aterminal identifier among a plurality of data in a plurality of terminaldata. Specifically, the arrangement order of terminal identifiersindicated by the terminal identifier field of an A-RTS frame mayindicate the arrangement order of MPDUs corresponding to a terminalindicated by a terminal identifier among a plurality of MPDUs in pluralterminal A-MPDUs. For example, when the terminal identifier field of anA-RTS frame includes terminal identifiers in the order of the terminalidentifier for a first terminal and the terminal identifier for a secondterminal, an MPDU including data for the first terminal may be locatedfirst and an MPDU for the second terminal may be located thereafter inplural terminal A-MPDUs. In another specific embodiment, an A-RTS framemay include offset information indicating the locations of theidentifier of a terminal and data corresponding to a correspondingterminal. For example, when offset information for the first terminalindicates 0 byte and offset information for the second terminalindicates 12 bytes, an MPDU including data for the second terminal maybe located after 12 bytes from the header of the plural terminalA-MPDUs.

The A-RTS frame may include a duration field indicating a value forupdating a value of a Network Allocation Vector (NAV) as in a typicalMac frame format. The value of the duration field may be determinedbased on the transmission time of an A-RTS frame and the transmissiontime of a plurality of terminal data. Specifically, the value of theduration field may be the sum of the transmission time of an A-RTSframe, SIFS, the transmission time of a CTS frame, the transmission timeof a plurality of terminal data, SIFS, and the transmission time of anACK frame.

In addition, an A-RTS frame may be implemented in consideration ofcompatibility with a legacy terminal that does not support an embodimentof the present invention. A conventional RTS frame includes a framecontrol field indicating information on frame control, a duration fieldindicating a value for updating the value of NAV, an RA field indicatingthe address of a terminal for receiving the data, a TA field indicatingthe address of a terminal for transmitting data, and a FCS fieldincluding a cyclic redundancy check (CRC) value for error detection. Atthis point, the TA field may be the address of a terminal that transmitsa plurality of terminal data. Specifically, the TA field may be theaddress of an access point that transmits a plurality of terminal data.At this point, the A-RTS frame may insert additional information afterthe FCS field of the conventional RTS frame. At this point, the legacyterminal decodes the FCS field and does not decode data included in theremaining A-RTS frames. Also, the value of the duration field, asdescribed above, may be determined based on the A-RTS transmission timeand the transmission time of a plurality of terminal data. At thispoint, a legacy terminal updates the NAV value with a value indicated bythe duration field. Therefore, a legacy terminal does not transmit datauntil the transmission of a plurality of terminal data is completed.Also, a group identifier for identifying a group representing aplurality of terminals for receiving plural terminal A-RTSs may beinserted in an existing RA field. At this point, the group identifiermay be the same as the group identifier indicating a plurality ofterminals receiving the plurality of terminal data or the groupidentifier indicating a plurality of terminals receiving an OFDMAsignal. When a value of an existing RA field indicates a groupidentifier, a terminal supporting an embodiment of the present inventionmay recognize an A-RTS frame. Therefore, a terminal supporting anembodiment of the present invention may decode a field after theconventional FCS field. In a specific embodiment, the structure of theA-RTS frame may be the same as that of FIG. 12 . Specifically, the A-RTSframe includes a Number of STAs field indicating the number of receptionterminals after the conventional FCS field, a terminal identifier fieldindicating a terminal identifier identifying a terminal receiving anA-MPDU, and an additional FCS field for error detection. At this point,the terminal identifier field may be divided into subfields by a numberindicated by the number field of a terminal. Additionally, as describedabove, the terminal identifier filed may indicate the address of aterminal. In addition, the terminal identifier field may indicate an AIDfor identifying an association between a terminal and a terminal.Further, an additional FCS field may be a value obtained by calculatinga CRC value of a field located after an existing FCS field.

FIGS. 13 to 20 are views illustrating that an access point transmitsdata to a plurality of stations through a frame indicating thetransmission preparation of a plurality of terminal data according toanother embodiment of the present invention.

A transmission terminal may transmit the A-RTS frame described above tothe primary channel and a conventional RTS frame to the remainingavailable channels. The specific operation may be as follows. Thetransmission terminal may collect data to be transmitted for apredetermined time. Such a predetermined time may be referred to as aData Accumulation Timer. At this point, the transmission terminal maywait without transmitting data even if a channel is in an idle stateduring the Data Accumulation Timer. After collecting data to betransmitted, the transmission terminal obtains a channel to be used intransmission according to a contention method. Specifically, when achannel is in an idle state for a predetermined time, the transmissionterminal transmits an A-RTS to a primary channel after waiting for acontention window value and transmits an RTS frame to a plurality ofremaining available channels. As described above, the determining of theavailable channel may determine whether the channel is in an idle statefor a predetermined time. At this point, the predetermined time may be aPIFS. In addition, the RTS frame serves to prevent the reception ofother terminals. The reception terminal may obtain information of aplurality of terminal data to be transmitted through the A-RTS frametransmitted through the primary channel. The reception terminal maytransmit a CTS frame. Specifically, the reception terminals may transmita CTS frame through an allocated channel. At this point, the receptionterminal may determine a channel allocated to the reception terminalbased on an A-RTS frame. Specifically, the reception terminal maydetermine a channel allocated to the reception terminal based on theterminal identifier arrangement order of the terminal identifier fieldof an A-RTS frame. In another specific embodiment, the receptionterminal may determine a channel allocated to the reception terminalbased on an RTS frame transmitted through a secondary channel.Specifically, when an RTS frame indicating that there is data to bereceived by the reception terminal together with the A-RTS frame of theprimary channel, the reception terminal may determine that the channelto which the RTS frame is transmitted is allocated to the receptionterminal. In addition, if the RTS frame indicating that there is data tobe received by the reception terminal other than the A-RTS frame is notreceived, the reception terminal may determine that the primary channelis allocated to the reception terminal. In addition, the receptionterminal may check whether a channel is available before transmittingthe CTS frame. Specifically, the reception terminal may determine that achannel is available when the channel is in an idle state for apredetermined time. At this point, the predetermined time may be anSIFS. In a specific embodiment, if the reception terminal has aninsufficient time to perform transmission through a transmissionoperation during a reception operation, the predetermined time may bethe sum of an SIFS and a PIFS. The transmission terminal may transmit aplurality of terminal data to a terminal that transmitted a CTS frame.The reception terminal transmits an ACK frame through a channelallocated to the reception terminal. At this point, as described above,the reception terminal may determine a channel allocated to thereception terminal based on an A-RTS frame. In another specificembodiment, the reception terminal may determine a channel allocated tothe reception terminal based on a plurality of terminal data.Specifically, the reception terminal may determine a channel allocatedto the reception terminal based on the headers of a plurality ofterminal data. Specifically, the reception terminal may determine achannel allocated to the reception terminal based on the terminalidentifier field of the headers of a plurality of terminal data.Specifically, the reception terminal may determine a channel allocatedto the reception terminal based on the terminal identifier field of theheaders of a plurality of terminal data. For example, when the headersof a plurality of terminal data includes the identifier of a terminal inthe order of the identifier of the first station and the identifier ofthe second station, the reception terminal may determine that thetransmission terminal allocates the first channel among the availablechannels to the first station and allocates the next channel to thesecond station. Further, the reception terminal may determine a channelallocated to the reception terminal based on the arrangement order ofthe plurality of data in the plurality of terminal data. Specifically,the reception terminal may decode a plurality of terminal data, anddetermine a channel allocated to the reception terminal by checking thearrangement order of a plurality of data in the plurality of terminaldata. For example, when plural terminal A-MPDUs include MPDUs in theorder of the MPDU for the first station and the MPDU for the secondstation, the reception terminal may determine that the first channelamong the available channels is allocated to the first station and thenext channel is allocated to the second station.

FIG. 13 is a view illustrating that an access point transmits pluralterminal A-MPDUs to a plurality of stations according to anotherembodiment of the present invention when the number of availablechannels is the same as the number of stations receiving the pluralterminal A-MPDUs.

In the embodiment of FIG. 13 , a transmission terminal is an accesspoint. The first station, the second station, the third station, thefourth station, and the fifth station receive plural terminal A-MPDUsfrom the access point. As described above, the access point transmitsthe A-RTS frame through the primary channel. The access point alsotransmits the RTS frame through an available secondary channel. Thefirst station, the second station, the third station, the fourthstation, and the fifth station transmit the CTS frame through theallocated channel as described above. At this point, the first station,the second station, the third station, the fourth station, and the fifthstation may determine the channel allocated to the first station, thesecond station, the third station, the fourth station, and the fifthstation based on the A-RTS frame. Specifically, the first station, thesecond station, the third station, the fourth station, and the fifthstation may determine the allocated channel based on the arrangementorder of the terminal identifier fields in the A-RTS frame. In addition,the first station transmits the CTS frame through the primary channelPrimary CH, the second station transmits the CTS frame through the firstsecondary channel Secondary CH #1, the third station transmits CTS framethrough the second secondary channel Secondary CH #2, the fourth stationtransmits CTS frame through the third secondary channel Secondary CH #3,and the fifth station transmits CTS frame through the fourth secondarychannel Secondary CH #4. The access point transmits plural terminalA-MPDUs through the primary channel Primary CH, the first secondarychannel Secondary CH #1, the second secondary channel Secondary CH #2,the third secondary channel Secondary CH #3, and the fourth secondarychannel Secondary CH #4. In addition, the first station, the secondstation, the third station, the fourth station, and the fifth stationtransmit an ACK frame through the allocated channel. The first stationtransmits the ACK frame through the primary channel Primary CH, thesecond station transmits the ACK frame through the first secondarychannel Secondary CH #1, the third station transmits ACK frame throughthe second secondary channel Secondary CH #2, the fourth stationtransmits ACK frame through the third secondary channel Secondary CH #3,and the fifth station transmits ACK frame through the fourth secondarychannel Secondary CH #4.

FIG. 14 is a view illustrating that an access point transmits pluralterminal A-MPDUs to a plurality of stations according to anotherembodiment of the present invention when the number of stationsreceiving the plural terminal A-MPDUs is greater than the number ofavailable channels.

When the number of reception terminals is greater than the number ofavailable channels, the transmission terminal may divide a plurality ofterminal data and transmit the divided plurality of terminal data in aplurality of times. This is because the transmission terminal lacks achannel through which the CTS frame and the ACK frame are received fromthe reception terminal. Specifically, a transmission terminal may firsttransmit a plurality of terminal data to a plurality of terminalscorresponding to the number identical to the number of availablechannels. Thereafter, when the plurality of terminals receiving theplurality of terminal data transmit an ACK frame, the remainingterminals that do not receive the plurality of terminal data maytransmit a CTS frame after a predetermined time from the transmission ofthe ACK frame. At this point, the predetermined time may be an SIFS.After receiving the CTS frame, the transmission terminal may transmit aplurality of terminal data to the terminal that transmitted the CTSframe. In addition, the transmission terminal may allocate an availablechannel to the reception terminal in a round robin manner. In addition,the transmission terminal may allocate a primary channel first to thereception terminal among an available primary channel and secondarychannel. In addition, the transmission terminal may allocate a secondarychannel having a small index first to the reception terminal amongavailable secondary channels.

In the embodiment of FIG. 14 , the access point transmits pluralterminal A-MPDUs to the first station, the second station, the thirdstation, the fourth station, the fifth station, the sixth station, andthe seventh station. At this point, the access point allocates a channelin a round robin manner. Specifically, the access point allocates theprimary channel Primary CH to the first station, the first secondarychannel Secondary CH #1 to the second station, the second secondarychannel Secondary CH #2 to the third station, the third secondarychannel Secondary CH #3 to the fourth station, the fourth secondarychannel Secondary CH #4 to the fifth station, the primary channelPrimary CH to the sixth station, and the first secondary channelSecondary CH #1 to the seventh station. The first station, the secondstation, the third station, the fourth station, and the fifth stationreceive plural terminal A-MPDUs through the above-described process andtransmits an ACK frame through the allocated channel. After apredetermined time after the ACK frame is transmitted, the sixth stationand the seventh station transmit a CTS frame to the allocated channel.At this point, the predetermined time may be an SIFS. The access pointreceiving a CTS frame from the sixth station and the seventh stationtransmits plural terminal A-MPDUs to the sixth station and the seventhstation.

FIG. 15 is a view illustrating that an access point transmits pluralterminal A-MPDUs to a plurality of stations according to anotherembodiment of the present invention when there is no available channel.

A transmission terminal does not allocate a channel, which is being usedby another terminal and thus is unavailable, to a reception terminal.Specifically, a transmission terminal does not transmit an RTS frame andan A-RTS frame through a channel that the other terminal uses and thusis unavailable. However, the reception terminal may determine whetherall the channels are available before sending the CTS frame. At thistime, if a channel not allocated by the transmission terminal isavailable, the reception terminal may transmit the CTS frame through thecorresponding channel. However, the reception terminal may determine achannel allocated by the transmission terminal based on availablechannels before sending the CTS frame. Specifically, if an availablechannel when the transmission terminal transmits the A-RTS frame is theprimary channel and the second secondary channel and an availablechannel before the reception terminal transmits the CTS frame is theprimary channel, the first secondary channel, and the second secondarychannel, the reception terminal may determine the order of the channelsthat the transmission terminal allocates to the reception terminal asthe primary channel, the first secondary channel, and the secondsecondary channel. The reception terminal may determine whether achannel is available when the channel is in an idle state for apredetermined time. Specifically, the predetermined time may be an SIFS.In another specific embodiment, the predetermined time may be the sum ofan SIFS and a PIFS.

In the embodiment of FIG. 15 , the access point allocates to a stationthe remaining channels other than the third secondary channel SecondaryCH #3 currently used by another terminal. The access point allocates theprimary channel Primary CH to the first station, the first secondarychannel Secondary CH #1 to the second station, the second secondarychannel Secondary CH #2 to the third station, the fourth secondarychannel Secondary CH #4 to the fourth station, the primary channelPrimary CH to the fifth station, the first secondary channel SecondaryCH #1 to the sixth station, and the second secondary channel SecondaryCH #2 to the seventh station. The first station, the second station, thethird station, and the fourth station receive plural terminal A-MPDUsthrough the above-described process and transmit an ACK frame throughthe allocated channel. After a predetermined time after the ACK frame istransmitted, the fifth station, the six station, and the seventh stationtransmit a CTS frame to the allocated channel. At this point, thepredetermined time may be an SIFS. The access point receiving a CTSframe from the fifth station, the sixth station, and the seventhstation, transmits plural terminal A-MPDUs to the fifth station, thesixth station, and the seventh station.

In the embodiments of FIGS. 14 to 15 described above, when the number ofreception terminals is larger than the number of available channels, aCTS frame is received as many as the number of available channels fromthe reception terminal and a plurality of terminal data is transmittedfirst to the reception terminal that transmits the CTS frame.Thereafter, the CTS frame is required to be received from the remainingreception terminals, and a plurality of terminal data is required to betransmitted to the reception terminal that transmitted the CTS frame.Therefore, the plurality of terminal data is required to be divided andtransmitted. When a plurality of reception terminals transmit a controlframe to only one specified channel, since the CTS frame is receivedfrom all the reception terminals before the plurality of terminal datais transmitted, the plurality of terminal data may be transmitted at atime. At this point, the one specified channel may be the primarychannel. In addition, the transmission terminal may transmit an A-RTSframe to one specified channel. Specifically, a plurality of receptionterminals may transmit a CTS frame to one specified channel. At thistime, since a plurality of reception terminals are not able to transmitCTS frames at the same time, the plurality of reception terminals maysequentially transmit the CTS frames. Specifically, the receptionterminal may transmit a CTS frame based on a predetermined transmissionorder between a plurality of reception terminals. At this point, thereception terminal may determine the order of transmitting CTS framesbased on an A-RTS frame. Specifically, the reception terminal maytransmit a CTS frame based on the arrangement order of the terminalidentifiers in the terminal identifier fields included in the A-RTSframe. In a specific embodiment, the reception terminal may determinethe arrangement order of the terminal identifiers in the terminalidentifier fields included in the A-RTS frame based on the CTS frametransmission order of a terminal identified by the terminal identifier.For example, if the identifier of the first station, the identifier ofthe second station, and the identifier of the third station are includedin this order in the terminal identifier field of the A-RTS frame, thefirst station transmits the CTS frame first, and then after the secondstation transmits the CTS frame, the third station may transmit the CTSframe. When a CTS frame in the latest order is transmitted, thetransmission terminal may transmit an RTS frame to the remainingavailable channels other than one channel specified for allowing thetransmission terminal to transmit a control frame. The determining of anavailable channel may be made based on whether a channel is in an idlestate for a predetermined time. At this point, the predetermined timemay be an SIFS. Additionally, in another specific embodiment, thepredetermined time may be the sum of an SIFS and a PIFS. Thetransmission terminal may reserve an available channel through thetransmission of such an RTS and transmit a plurality of terminal data.The transmission terminal may transmit a plurality of terminal dataafter receiving the last CTS frame. The reception terminal may receivean A-MPDU and transmit an ACK frame through one specified channel. Atthis point, the reception terminal may transmit an ACK frame based on apredetermined transmission order between a plurality of receptionterminals, such as the transmission of a CTS frame. Specifically, thereception terminal may determine the order of transmitting ACK framesbased on an A-RTS frame. Specifically, the reception terminal maytransmit an ACK frame based on the arrangement order of the terminalidentifiers in the terminal identifier fields in the A-RTS frame. In aspecific embodiment, the reception terminal may determine thearrangement order of the terminal identifiers in the terminal identifierfields included in the A-RTS frame based on the ACK frame transmissionorder of a terminal identified by the terminal identifier. At thispoint, a value that the duration field of each ACK frame has may be thesum of the transmission time of ACK frames to be transmitted after thetransmission of the corresponding ACK frame and a standby time accordingthereto. At this point, the standby time may be an SIFS. Additionally,when an ACK frame is not received from one reception terminal, thetransmission terminal transmits data to a reception terminal that didnot transmit an ACK frame after the time point that the last ACK frameis to be received. At this point, data transmitted to the receptionterminal may include only data for a corresponding terminal. In anotherspecific embodiment, data transmitted to the reception terminal may beplural terminal A-MPDUs.

In the embodiment of FIG. 16 , a transmission terminal is an accesspoint. The access point transmits plural terminal A-MPDUs to the firststation, the second station, the third station, the fourth station, andthe fifth station. The access point transmits an A-RTS frame through theprimary channel Primary CH. The first station, the second station, thethird station, the fourth station, and the fifth station transmit a CTSframe through the primary channel Primary CH. At this point, the firststation, the second station, the third station, the fourth station, andthe fifth station transmit CTS frames sequentially through the primarychannel Primary CH. As described above, the reception terminal maydetermine the order of transmitting CTS frames based on an A-RTS frame.When the fifth station transmits a CTS frame, the access point transmitsan RTS frame through all the available channels other than a channelthat the fifth station transmits the CTS frame. Thereafter, the accesspoint transmits plural terminal A-MPDUs. The first station, the secondstation, the third station, the fourth station, and the fifth stationtransmit ACK frames sequentially through the primary channel Primary CH.As described above, a value that the duration field of each ACK framehas may be the sum of the transmission time of ACK frames to betransmitted after the transmission of the corresponding ACK frame and anSIFS standby time according thereto.

In the embodiment of FIG. 16 , even when the number of receptionterminals is greater than the number of available channels, pluralterminal A-MPDUs may be transmitted at once. However, if transmission isperformed as shown in FIG. 16 , it may take a long time to receive anACK frame. Therefore, there is a need for a method of reducing the timeuntil a transmission terminal receives an ACK frame after datatransmission. This will be described with reference to FIGS. 17 and 18 .

FIG. 17 is a view illustrating that an access point transmits pluralterminal A-MPDUs to a plurality of stations according to anotherembodiment of the present invention when a plurality of stationstransmit CTS frames through only one specified channel and transmit ACKframes through different channels at the same time.

As described above, a plurality of reception terminals may transmit aCTS frame through only one specified channel. That is, a plurality ofreception terminals receiving a plurality of terminal data from the sametransmission terminal may transmit a CTS frame through one specifiedchannel. At this point, the order of transmitting CTS frames may be thesame as that described through the embodiment of FIG. 16 . In addition,the plurality of reception terminals may transmit ACK frames at the sametime through a channel allocated to each terminal. In addition, asdescribed in the embodiments of FIGS. 12 to 15 , the reception terminalmay determine a channel allocated to the reception terminal based on anA-RTS frame. In another specific embodiment, as described in theembodiments of FIGS. 12 to 15 , the reception terminal may determine achannel allocated to the reception terminal based on a plurality ofterminal data.

In the embodiment of FIG. 17 , the access point transmits pluralterminal A-MPDUs to the first station, the second station, the thirdstation, the fourth station, and the fifth station. The access pointtransmits an A-RTS frame through the primary channel Primary CH. Thefirst station, the second station, the third station, the fourthstation, and the fifth station transmit CTS frames sequentially. At thispoint, the first station, the second station, the third station, thefourth station, and the fifth station, as described above, may determinethe transmission order based on an A-RTS frame. As described above, thereception terminal may determine the order of transmitting CTS framesbased on an A-RTS frame. When the fifth station transmits a CTS frame,the access point transmits an RTS frame through all the availablechannels other than a channel that the fifth station transmits the CTSframe. Thereafter, the access point transmits plural terminal A-MPDUs.The first station, the second station, the third station, the fourthstation, and the fifth station transmit an ACK frame at the same timethrough each specified channel. Through such an operation, the time thatthe transmission terminal receives an ACK frame from the receptionterminal may be shortened.

FIG. 18 is a view illustrating that an access point transmits pluralterminal A-MPDUs according to an embodiment of the present inventionwhen one channel is unavailable and a plurality of stations transmit CTSframes through only one specified channel and transmit ACK framesthrough different channels at the same time.

As described above, when a CTS frame is transmitted lastly, thetransmission terminal may transmit an RTS frame through all theavailable channels other than a channel in which the CTS frame istransmitted. At this time, the transmission terminal may determinewhether all the channels are available or not. Specifically, it may bedetermined that a channel is available when the channel is in an idlestate for a predetermined time. At this point, the predetermined timemay be a PIFS. In another specific embodiment, the predetermined timemay be the sum of an SIFS and a PIFS. Therefore, the transmissionterminal transmits an RTS frame through a channel except a channel beingused by another user. In addition, the transmission terminal maytransmit a plurality of terminal data through an available channelexcept for an unavailable channel being used by another user.

In addition, as described above, a plurality of reception terminals maysimultaneously transmit ACK frames through each specified channel. Atthis time, if the number of available channels is smaller than thenumber of reception terminals, the reception terminal may determine aspecified channel and a transmission order based on an A-RTS frame.Specifically, if the number of available channels is smaller than thenumber of reception terminals, the reception terminal may determine aspecified channel and a transmission order based on the order of theterminal identifies in the terminal identifier field of an A-RTS frame.In a specific embodiment, the reception terminal may determine aspecified channel and a transmission order based on that a specifiedchannel is allocated to a reception terminal identified by a terminalidentifier in the round-robin manner according to the order of theterminal identifiers in the terminal identifier fields of the A-RTSframe. For example, if an available channel is a primary channel and theterminal identifier field of an A-RTS frame includes the identifier ofthe first station, the identifier of the second station, and theidentifier of the third station in this order, the first station maytransmit the ACK frame through the primary channel and the secondstation may transmit the ACK frame through the first secondary channel.Thereafter, the third station may transmit an ACK frame through theprimary channel.

In another specific embodiment, if the number of available channels issmaller than the number of reception terminals, the reception terminalmay determine a specified channel and a transmission order based on aplurality of terminal data. Specifically, if the number of availablechannels is smaller than the number of reception terminals, thereception terminal may determine a specified channel and a transmissionorder based on the order of the terminal identifies in the terminalidentifier fields of the headers of a plurality of terminal data frames.In a specific embodiment, the reception terminal may determine aspecified channel and a transmission order based on that a specifiedchannel and a transmission order are allocated to a reception terminalidentified by a terminal identifier in the round-robin manner accordingto the order of the terminal identifiers in the terminal identifierfields of the headers of a plurality of terminal data. For example, ifan available channel is a primary channel and a first secondary channeland the terminal identifier fields of the headers of a plurality ofterminal data include the identifier of the first station, theidentifier of the second station, and the identifier of the thirdstation in this order, the first station may transmit the ACK framethrough the primary channel and the second station may transmit the ACKframe through the first secondary channel. Thereafter, the third stationmay transmit an ACK frame through the primary channel. Additionally, ifthe number of available channels is smaller than the number of receptionterminals, the reception terminal may determine a specified channel anda transmission order based on the arrangement order of a plurality ofdata in a plurality of terminal data frames. In a specific embodiment,the reception terminal may determine a specified channel and atransmission order based on that a specified channel and a transmissionorder are allocated to a reception terminal identified by a terminalidentifier in the round-robin manner according to the arrangement orderof a plurality of data in a plurality of terminal data. For example, ifan available channel is a primary channel and a first secondary channeland plural terminal A-MPDUs include an MPDU for the first station, anMPDU for the second station, and an MPDU for the third station in thisorder, the first station may transmit the ACK frame through the primarychannel and the second station may transmit the ACK frame through thefirst secondary channel.

In the embodiment of FIG. 18 , the access point transmits pluralterminal A-MPDUs to the first station, the second station, the thirdstation, the fourth station, and the fifth station. The access pointtransmits an A-RTS frame through the primary channel Primary CH. Thefirst station, the second station, the third station, the fourthstation, and the fifth station transmit CTS frames sequentially. At thispoint, the first station, the second station, the third station, thefourth station, and the fifth station, as described above, may determinethe transmission order based on an A-RTS frame. When the fifth stationtransmits a CTS frame, the access point transmits an RTS frame throughall the available channels other than a channel that the fifth stationtransmits the CTS frame. In the embodiment of FIG. 18 , since the thirdsecondary channel Secondary CH #3 is not in the idle state, an RTS frameis transmitted through a channel except for the third secondary channelSecondary CH #3. Thereafter, the access point transmits plural terminalA-MPDUs. At this time, since the third secondary channel Secondary CH #3is not in an idle state, the transmission terminal transmits pluralterminal A-MPDUs through the remaining channels except for the thirdsecondary channel Secondary CH #3. The first station, the secondstation, the third station, and the fourth station transmit an ACK frameat the same time through each specified channel. The fifth stationtransmits an ACK frame through the primary channel Primary CH after apredetermined time after the first station transmits the ACK frame. Atthis point, the predetermined time may be an SIFS. Through such anoperation, the time that the transmission terminal receives an ACK framefrom the reception terminal may be shortened.

As described above, according to the 802.11ac standard prior to theembodiment of the present invention, communication between terminals isperformed through a primary channel and a secondary channel extendingthe primary channel. Accordingly, in order for one terminal tosimultaneously support data for a terminal according to the related artand a terminal supporting the embodiment of the present invention, atransmission terminal is required to transmit plural terminal A-MPDUsthrough another available channel other than a primary channel and asecondary channel extending the primary channel. This will be describedwith reference to FIGS. 19 and 20 .

FIG. 19 is a view illustrating that an access point according to anotherembodiment of the present invention transmits data to a terminal thatdoes not support an embodiment of the present invention and a terminalthat supports an embodiment of the present invention.

A transmission terminal may transmit a plurality of terminal datathrough the remaining available channels other than a primary channeland a secondary channel extending the primary channel. At this time, thetransmission terminal may transmit an A-RTS frame through the firstsecondary channel among the remaining available channels other than aprimary channel and a secondary channel extending the primary channel.In addition, the transmission terminal may transmit only an A-RTS frameand transmit a plurality of terminal data immediately without a responsefor a CTS frame. Specifically, when a predetermined time elapses afteran A-RTS frame is transmitted, the transmission terminal may transmit aplurality of terminal data through a primary channel and an availablechannel not the primary channel. At this point, the predetermined timemay be an SIFS. In addition, the transmission terminal may determinethat a channel is available when the channel is in an idle state for apredetermined time. In this case, collision may occur with other datatransmission due to a hidden node or the like. However, there is anadvantage that the time consumption occurring in the transmissionprocess of a CTS frame may be reduced. Each of the plurality ofreception terminals may transmit an ACK frame through a channelallocated to each reception terminal as in the above-describedembodiment.

In the embodiment of FIG. 19 , the access point transmits data to thethird station and the fifth station, which do not support an embodimentof the present invention, and the first station, the second station, thefourth station, the sixth station, and the seventh station, whichsupport an embodiment of the present invention. In detail, the accesspoint transmits data to the third station and the fifth station throughthe primary channel Primary CH. Additionally, the access point transmitsan A-RTS frame through the first secondary channel Secondary CH #1,which is an available channel that is not the primary channel Primary CHand a secondary channel extending the primary channel Primary CH. Theaccess point transmits plural terminal A-MPDUs when an SIFS elapsesafter the A-RTS frame was transmitted. At this time, since the fourthsecondary channel Secondary CH #4 is in use by another terminal, theaccess point may transmit plural terminal A-MPDUs through the firstsecondary channel Secondary CH #1, the second secondary channelSecondary CH #2, the third secondary channel Secondary CH #3, the fifthsecondary channel Secondary CH #5, the sixth secondary channel SecondaryCH #6, and the seventh secondary channel CH #7, excluding the fourthsecondary channel CH #4. The first station, the second station, thefourth station, the sixth station, and the seventh station transmit anACK frame to the access point according to an allocated channel.

FIG. 20 is a view illustrating that an access point according to anotherembodiment of the present invention transmits data to a terminal thatdoes not support an embodiment of the present invention and a terminalthat supports an embodiment of the present invention.

As described above, a transmission terminal may transmit a plurality ofterminal data through the remaining available channels other than aprimary channel and a secondary channel extending the primary channel.At this time, the transmission terminal may transmit an A-RTS framethrough the first secondary channel among the remaining availablechannels other than a primary channel and a secondary channel extendingthe primary channel. Additionally, the transmission terminal maytransmit an A-RTS frame to all available channels other than a primarychannel and a secondary channel extending the primary channel aftertransmitting an RTS frame. In another specific embodiment, thetransmission terminal may transmit an RTS frame to all availablechannels other than a primary channel and a secondary channel extendingthe primary channel while transmitting an A-RTS frame. In addition, thetransmission terminal may transmit a plurality of terminal data througha channel available when transmitting the plurality of terminal data inaddition to a channel that received a CTS frame. Specifically, thetransmission terminal may transmit a plurality of terminal data througha channel in an idle state for a predetermined time when transmittingthe plurality of terminal data in addition to a channel that received aCTS frame. At this point, the predetermined time may be a PIFS. Forthis, the transmission terminal may sense a state of a channel that doesnot receive a CTS frame.

In the embodiment of FIG. 20 , the access point transmits data to thethird station and the fifth station, which do not support an embodimentof the present invention, and the first station, the second station, thefourth station, the sixth station, and the seventh station, whichsupport an embodiment of the present invention. In detail, the accesspoint transmits data to the third station and the fifth station throughthe primary channel Primary CH. Additionally, the access point transmitsan A-RTS frame through the first secondary channel Secondary CH #1,which is an available channel that is not the primary channel Primary CHand a secondary channel extending the primary channel Primary CH. Whenan SIFS elapses from the transmission of an A-RTS frame, the accesspoint transmits an RTS frame to the first station, the second station,the fourth station, the sixth station, and the seventh station. At thispoint, the access point transmits an RTS frame for each station througha channel allocated to each station. In addition, a CTS frame istransmitted to the first station, the second station, the fourthstation, the sixth station, and the seventh station. The access pointdetermines whether a channel through which a CTS frame is transmittedand the remaining channels other than the primary channel are available.It is determined that the fourth secondary channel Secondary CH #4 andthe seventh secondary channel Secondary CH #7 are available and thus,the access point transmits plural terminal A-MPDUs to the first station,the second station, the fourth station, the sixth station, and theseventh station through the first secondary channel Secondary CH #1, thesecond secondary channel Secondary CH #2, the third secondary channelSecondary CH #3, the fourth secondary channel Secondary CH #4, the fifthsecondary channel Secondary CH #5, the sixth secondary channel SecondaryCH #6, and the seventh secondary channel Secondary CH #7. The firststation, the second station, the fourth station, the sixth station, andthe seventh station transmit an ACK frame to the access point accordingto an allocated channel.

In the above-described embodiments, a channel is reserved through an RTSframe or an A-RTS frame, after that a plurality of terminal data istransmitted. In such a case, it is possible to prevent data collision bystably reserving a channel through which plural terminal A-MPDUs aretransmitted. However, it takes a long time to transmit an RTS frame oran A-RTS frame, so that data transmission may be delayed. Therefore,when the transmission terminal transmits a plurality of terminal datawithout securing a channel through an RTS frame or an A-RTS, the risk ofcollision with another data transmission may be high, but thetransmission time point of a plurality of terminal data may be advanced.This will be described with reference to FIGS. 21 to 23 .

FIGS. 21 to 23 are views illustrating that an access point transmitsdata to a plurality of stations without transmitting a frame indicatingthe transmission preparation of a plurality of terminal data accordingto another embodiment of the present invention.

FIG. 21 is a view illustrating that an access point according to anotherembodiment of the present invention transmits plural terminal A-MPDUs toa plurality of stations without transmitting a frame indicating datatransmission preparation.

A transmission terminal waits for a predetermined time. If acorresponding channel is in an idle state for a predetermined time, thetransmission terminal performs a contention procedure for random backoffwithin a contention window value. At this point, the predetermined timemay be a DIFS. In another specific embodiment, the predetermined timemay be an Arbitration Inter-frame Space (AIFS). In addition, acorresponding channel may be a primary channel. After a contentionprocedure, the transmission terminal may transmit a plurality ofterminal data through an available channel without the transmission of aframe indicating that data transmission is prepared. Specifically, thetransmission terminal may transmit a plurality of terminal data throughan available channel without the transmission of an RTS frame and anA-RTS frame. At this time, the transmission terminal may determinewhether a corresponding channel is in an idle state for a predeterminedtime. At this point, the predetermined time may be a PIFS.

A plurality of reception terminals may transmit an ACK frame through onespecified channel. Specifically, the reception terminal may transmit anACK frame based on a predetermined transmission order between aplurality of reception terminals. At this point, the reception terminalmay determine the transmission order of ACK frames based on the headerof the plurality of terminal data. For example, the reception terminalmay determine its transmission order based on the terminal identifierfield of the headers of a plurality of terminal data. At this time, thereception terminal may determine the arrangement order of the terminalidentifiers in the terminal identifier fields of the plurality ofterminal data headers as the order of transmitting an ACK frame of thereception terminal identified by the terminal identifier among theplurality of reception terminals. For example, when the headers of aplurality of terminal data includes the identifier of a terminal in theorder of the identifier of the first station and the identifier of thesecond station, the reception terminal may determine that the firststation transmits the ACK frame and after that, the second stationtransmits the ACK frame. Further, the reception terminal may determinethe transmission order of ACK frames based on the arrangement order ofthe plurality of data in the plurality of terminal data. Specifically,the reception terminal may decode a plurality of terminal data to checkthe arrangement order of a plurality of data in the plurality ofterminal data, and determine the arrangement order of the plurality ofdata as an order in which a data related reception terminal among aplurality of terminals transmits an ACK frame. For example, when pluralterminal A-MPDUs include an MPDU for the first station and an MPDU forthe second station in this order, the reception terminal may determinethat the first station transmits the ACK frame and after that, thesecond station transmits the ACK frame. Additionally, the one specifiedchannel may be the primary channel. In another specific embodiment, onespecified channel may be any one secondary channel other than asecondary channel extending the primary channel among a plurality ofsecondary channels. Additionally, when a plurality of receptionterminals are redundantly allocated to the same channel, a value thatthe duration field of each ACK frame has may be the sum of thetransmission time of ACK frames to be transmitted after the transmissionof the corresponding ACK frame and a standby time according thereto. Atthis point, the standby time may be an SIFS.

In addition, as described in the embodiment of FIG. 16 , a value thatthe duration field of each ACK frame has may be the sum of thetransmission time of ACK frames to be transmitted after the transmissionof the corresponding ACK frame and a standby time according thereto. Atthis point, the standby time may be an SIFS.

In the embodiment of FIG. 21 , the access point transmits pluralterminal A-MPDUs to the first station, the second station, the thirdstation, the fourth station, and the fifth station. The access pointperforms a contention procedure. After the contention procedure, theaccess point may transmit plural terminal A-MPDUs through an availablechannel without the transmission of a frame indicating that datatransmission is prepared. Specifically, without the transmission of aframe indicating that data transmission is prepared, the access pointtransmits plural terminal A-MPDUs through the primary channel PrimaryCH, the first secondary channel Secondary CH #1, the second secondarychannel Secondary CH #2, the third secondary channel Secondary CH #3,and the fourth secondary channel Secondary CH #4. The reception terminaltransmits an ACK frame through the primary channel according to aspecified order. Specifically, in the order of the first station, thesecond station, the third station, the fourth station, and the fifthstation, an ACK frame is transmitted through the primary channel.

FIGS. 22 and 23 are views illustrating that an access point according toanother embodiment of the present invention transmits plural terminalA-MPDUs to a plurality of stations without transmitting a frameindicating data transmission preparation and the plurality of stationstransmit an ACK frame at the same time through a channel allocated toeach of the plurality of stations.

When a plurality of reception terminals transmit an ACK frame throughone specified channel, it takes a long time until a transmissionterminal receives all ACK frames. In order to solve this, as describedin the embodiments of FIGS. 17 and 18 , each of the plurality ofterminals may transmit an ACK frame through a channel allocated to eachreception terminal. The reception terminal may determine a channelallocated to the reception terminal based on a plurality of terminaldata. Specifically, the reception terminal may determine a channelallocated to the reception terminal based on the headers of a pluralityof terminal data. Specifically, the reception terminal may determine achannel allocated to the reception terminal based on the terminalidentifier field of the headers of a plurality of terminal data.Specifically, the reception terminal may determine a channel allocatedto the reception terminal based on the terminal identifier field of theheaders of a plurality of terminal data. In a specific embodiment, thereception terminal may determine the arrangement order of the terminalidentifiers in a plurality of terminal data headers as the arrangementorder of channels allocated to the reception terminal identified by theterminal identifier. For example, when the headers of a plurality ofterminal data includes the identifier of a terminal in the order of theidentifier of the first station and the identifier of the secondstation, the reception terminal may determine that the transmissionterminal allocates the first channel among the available channels to thefirst station and allocates the next channel to the second station.Further, the reception terminal may determine a channel allocated to thereception terminal based on the arrangement order of the plurality ofdata in the plurality of terminal data. Specifically, the receptionterminal may decode a plurality of terminal data, and determine achannel allocated to the reception terminal by checking the arrangementorder of a plurality of data in the plurality of terminal data. Forexample, when plural terminal A-MPDUs include the MPDU for the firststation and the MPDU for the second station in this order, the receptionterminal may determine that the first channel among the availablechannels is allocated to the first station and the next channel isallocated to the second station.

In another specific embodiment, if the number of available channels issmaller than the number of reception terminals, the reception terminalmay determine a specified channel and a transmission order based on aplurality of terminal data. Specifically, if the number of availablechannels is smaller than the number of reception terminals, thereception terminal may determine a specified channel and a transmissionorder based on the order of the terminal identifies in the terminalidentifier field of the headers of a plurality of terminal data frames.In a specific embodiment, the reception terminal may determine aspecified channel and a transmission order based on that a specifiedchannel and a transmission order are allocated to a reception terminalin the round-robin manner according to the order of the terminalidentifiers in the terminal identifier fields of the headers of aplurality of terminal data. For example, if an available channel is aprimary channel and a first secondary channel and the terminalidentifier fields of the headers of a plurality of terminal data includethe identifier of the first station, the identifier of the secondstation, and the identifier of the third station in this order, thefirst station may transmit the ACK frame through the primary channel andthe second station may transmit the ACK frame through the firstsecondary channel. Thereafter, the third station may transmit an ACKframe through the primary channel. Additionally, when determining achannel allocated to the reception terminal, the reception terminal mayexclude an unavailable channel and determine the channel allocated tothe reception terminal. Additionally, if the number of availablechannels is smaller than the number of reception terminals, thereception terminal may determine a specified channel and a transmissionorder based on the arrangement order of a plurality of data in aplurality of terminal data. In a specific embodiment, the receptionterminal may determine a specified channel and a transmission orderbased on that a specified channel and a transmission order are allocatedto a reception terminal in the round-robin manner according to thearrangement order of a plurality of data in a plurality of terminaldata. For example, if an available channel is a primary channel and afirst secondary channel and plural terminal A-MPDUs include an MPDU forthe first station, an MPDU for the second station, and an MPDU for thethird station in this order, the first station may transmit the ACKframe through the primary channel and the second station may transmitthe ACK frame through the first secondary channel. Additionally, when aplurality of reception terminals are redundantly allocated to the samechannel, a value that the duration field of each ACK frame has may bethe sum of the transmission time of ACK frames to be transmitted afterthe transmission of the corresponding ACK frame and a standby timeaccording thereto. At this point, the standby time may be an SIFS.

In the embodiment of FIG. 22 , the access point transmits pluralterminal A-MPDUs to the first station, the second station, the thirdstation, the fourth station, and the fifth station. The access pointperforms a contention procedure. After the contention procedure, theaccess point may transmit plural terminal A-MPDUs through an availablechannel without the transmission of a frame indicating that datatransmission is prepared. Specifically, without the transmission of aframe indicating that data transmission is prepared, the access pointtransmits plural terminal A-MPDUs through the primary channel PrimaryCH, the first secondary channel Secondary CH #1, the second secondarychannel Secondary CH #2, the third secondary channel Secondary CH #3,and the fourth secondary channel Secondary CH #4. The reception terminaltransmits an ACK frame through an allocated channel. In detail, thefirst station transmits the ACK frame through the primary channelPrimary CH, the second station transmits the ACK frame through the firstsecondary channel Secondary CH #1, the third station transmits ACK framethrough the second secondary channel Secondary CH #2, the fourth stationtransmits ACK frame through the third secondary channel Secondary CH #3,and the fifth station transmits ACK frame through the fourth secondarychannel Secondary CH #4.

In the embodiment of FIG. 23 , the third secondary channel Secondary CH#3 is unavailable. Accordingly, without the transmission of a frameindicating that data transmission is prepared, the access pointtransmits plural terminal A-MPDUs through the primary channel PrimaryCH, the first secondary channel Secondary CH #1, the second secondarychannel Secondary CH #2, and the fourth secondary channel Secondary CH#4. In addition, the reception terminal transmits an ACK frame through achannel allocated to the reception terminal in a specified order. Atthis point, when determining a channel allocated to the receptionterminal, the reception terminal may exclude a channel, which is anunavailable channel and thus not allocated, and determine the channelallocated to the reception terminal. In detail, the first stationtransmits the ACK frame through the primary channel Primary CH, thesecond station transmits the ACK frame through the first secondarychannel Secondary CH #1, the third station transmits ACK frame throughthe second secondary channel Secondary CH #2, and the fourth stationtransmits ACK frame through the fourth secondary channel Secondary CH#4. After the transmission of the first station, the fifth stationtransmits an ACK frame through the primary channel Primary CH. At thispoint, the value of the duration field of the ACK frame transmitted bythe first station may be the sum of the ACK frame transmission time ofthe fifth station and an SIFS according thereto.

FIG. 24 is a ladder diagram illustrating an operation that a terminaltransmits data to a plurality of other terminals at the same timeaccording to an embodiment of the present invention.

A transmission terminal 500 receives data for a plurality of receptionterminals (S301). Specifically, the transmission terminal 500 maycollect data for a plurality of reception terminals to generate pluralterminal A-MPDUs. A plurality of terminal data may include a pluralityof terminal data headers for signaling data in the plurality of terminaldata. As described above, the plural terminal A-MPDUs may include aplurality of MPDUs. At this time, the first MPDU of the plurality ofMPDUs may be a header for signaling data included in the plural terminalA-MPDUs. Additionally, the headers of a plurality of terminal data mayinclude a group address for identifying a group that represents aplurality of reception terminals. Additionally, the headers of aplurality of terminal data may include information on a channel used bya wireless communication terminal and an MCS of a signal used in thechannel. In addition, the headers of a plurality of terminal data mayinclude user information indicating a relationship between a pluralityof data in the plurality of terminal data and a plurality of receptionterminals. Additionally, the user information may indicate a channelallocated to the plurality of reception terminals. The plurality ofreception terminals may transmit a control frame to the transmissionterminal through an allocated channel. At this point, the control framemay be a frame indicating the reception completion of data. At thispoint, the frame may be an ACK frame. In addition, the control frame maybe a frame indicating that data is able to be received. At this point,the frame may be a CTS frame.

The transmission terminal 500 transmits a plurality of terminal data tothe reception terminal 400 based on data for a plurality of receptionterminals (S303). Specifically, the transmission terminal 500 maytransmit plural terminal A-MPDUs to the reception terminal 400. Thereception terminal 400 receives a plurality of terminal data from thetransmission terminal 500. Specifically, the reception terminal 400 mayreceive plural terminal A-MPDUs from the transmission terminal 500. Thetransmission terminal 500 may transmit a frame indicating thepreparation of data transmission before transmitting a plurality ofterminal data. At this point, the frame indicating preparation may be anA-RTS frame indicating the transmission preparation of a plurality ofterminal data. At this point, the A-RTS frame may include a plurality ofterminal identifiers for identifying a plurality of reception terminalsand the number of the plurality of reception terminals. In addition, theframe indicating transmission preparation may be an RTS frame indicatingthat the data transmission for one terminal is ready. The receptionterminal 400 may transmit a frame indicating that data is able to bereceived to the transmission terminal 500. At this point, the frame maybe a CTS frame. The reception terminal 400, as described above, maytransmit a control frame relating to the transmission control of a MACframe through a channel allocated to the reception terminal 400. Asdescribed above, the reception terminal 400 may determine a channelallocated to the reception terminal based on an A-RTS frame.Specifically, the reception terminal 400 may determine a channelallocated to the reception terminal based on the arrangement order ofthe terminal identifiers in an A-RTS frame. In addition, the receptionterminal 400 may determine a channel allocated to the reception terminalbased on a plurality of terminal data. Specifically, a channel allocatedto the reception terminal 400 may be determined based on the arrangementorder of the terminal identifiers in a plurality of terminal data. Inaddition, the reception terminal 400 may determine a channel allocatedto the reception terminal based on the arrangement order of a pluralityof data in a plurality of terminal data. In addition, a plurality ofreception terminals including the reception terminal 400, as describedabove, may transmit a control frame relating to the transmission controlof a MAC frame through one specified transmission channel. At thispoint, the reception terminal 400 may transmit a control frame based ona transmission order between a plurality of reception terminals thattransmit the control frame. The reception terminal 400 may determine atransmission order based on an A-RTS frame. Specifically, the receptionterminal 400 may determine a transmission order based on the arrangementorder of the terminal identifiers in an A-RTS frame. In addition, thereception terminal 400 may determine a transmission order based on aplurality of terminal data. Specifically, a transmission order may bedetermined based on the arrangement order of the terminal identifiers ina plurality of terminal data. In addition, the reception terminal 400may determine a transmission order based on the arrangement order of aplurality of data in a plurality of terminal data. At this point, thecontrol frame may include a frame indicating that the reception ispossible. In addition, the control frame may include a frame indicatingthat the reception is completed.

The reception terminal 400 obtains data relating to the receptionterminal from a plurality of terminal data (S305). Specifically, thereception terminal 400 may obtain an MPDU relating to the receptionterminal from plural terminal A-MPDUs. The reception terminal 400 mayobtain an MPDU relating to the reception terminal based on userinformation indicating a relationship between a plurality of data in aplurality of terminal data included in the headers of the plurality ofterminal data and a plurality of reception terminals. Specifically, thereception terminal 400 may determine the location of an MPDU includingdata related to the reception terminal 400 based on the arrangementorder of the terminal identifiers in the headers of a plurality ofterminal data. In another specific embodiment, the reception terminal400 may obtain an MPDU relating to the reception terminal based on theterminal identifier field of an A-RTS frame. Specifically, the receptionterminal 400 may determine the location of an MPDU including datarelated to the reception terminal 400 based on the arrangement order ofthe terminal identifier fields in an A-RTS frame.

The reception terminal 400 transmits a frame indicating the receptioncompletion of a plurality of terminal data (S307). As described above,the reception terminal 400 may transmit a frame indicating receptioncompletion through a channel allocated to the reception terminal 400. Amethod of determining a channel allocated to a reception terminal may bethe same as that described in operation S303 for transmitting aplurality of terminal data to the reception terminal 400. In addition, aplurality of reception terminals including the reception terminal 400,as described above, may transmit a frame indicating the receptioncompletion through one transmission channel. At this point, thereception terminal 400 may transmit a frame indicating the receptioncompletion based on a transmission order between a plurality ofreception terminals that transmit the frame indicating the receptioncompletion. A method of determining a transmission order may be the sameas that described in operation S303 for transmitting a plurality ofterminal data to the reception terminal 400. The frame indicatingreception completion may be an ACK frame.

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from the spirit and scope of the present invention.For example, each component specifically shown in the embodiments may bemodified and implemented. It should be interpreted that differencesrelating to such modifications and application are included in the scopeof the present invention defined in the appended claims.

The invention claimed is:
 1. A wireless communication terminalcomprising: a transceiver; and a processor, wherein the processor isconfigured to: receive, through the transceiver, a first control framewhich reserves a channel for a transmission between an access point anda first plurality of wireless communication terminals, includes terminalidentifier fields, and includes information on each of channelsrespectively allocated to each of the first plurality of wirelesscommunication terminals, from the access point, wherein a receiveraddress of the first control frame is a group address which indicates asecond plurality of wireless communication terminals including the firstplurality of wireless communication terminals, wherein the terminalidentifier fields include a plurality of association identifiers,wherein each of the plurality of association identifiers respectivelyidentifies the each of the first plurality of wireless communicationterminals, and transmit, by using the transceiver, a second controlframe in response to the first control frame to the access point througha channel allocated to the wireless communication terminal which isindicated by the information when the wireless communication terminaldetermines that the channel allocated to the wireless communicationterminal is idle for a predetermined time and at least one of theterminal identifier fields indicates the wireless communicationterminal, wherein the first control frame includes a duration fieldwhich is used for setting a network allocation vector for thetransmission between the access point and the first plurality ofwireless communication terminals.
 2. A method of operating a wirelesscommunication terminal comprising: receiving a first control frame whichreserves a channel for a transmission between an access point and afirst plurality of wireless communication terminals, includes terminalidentifier fields, and includes information on each of channelsrespectively allocated to each of the first plurality of wirelesscommunication terminals, from the access point, wherein a receiveraddress of the first control frame is a group address which indicates asecond plurality of wireless communication terminals including the firstplurality of wireless communication terminals, wherein the terminalidentifier fields include a plurality of association identifiers,wherein each of the plurality of association identifiers respectivelyidentifies the each of the first plurality of wireless communicationterminals, and transmitting a second control frame in response to thefirst control frame to the access point through a channel allocated tothe wireless communication terminal which is indicated by theinformation when the wireless communication terminal determines that thechannel allocated to the wireless communication terminal is idle for apredetermined time and at least one of the terminal identifier fieldsindicates the wireless communication terminal, wherein the first controlframe includes a duration field which is used for setting a networkallocation vector for the transmission between the access point and thefirst plurality of wireless communication terminals.